Zinc metabolism is evaluated through a balance study to determine the requirements of healthy young adults. Subjects are given 4 incremental levels of zinc to supplement a basal intake. Zinc status is determined as a function of alterations in its concentration in plasma, erythrocytes, leukocytes, hair, sweat, saliva, urine and feces. The long-term purposes of this program is to define more adequately zinc allowances for healthy subjects and to recognize chronic states of sub-acute Zinc deficiency so that appropriate zinc supplementation can be instituted to overcome this condition.